As a background-art technique of this type, there is a technique disclosed in Patent Literature 1. The background-art technique is made up of a hydraulic excavator. The hydraulic excavator has an undercarriage, an upper structure which is disposed on the undercarriage, and a work machine, that is, a work device which is attached to the upper structure so as to be rotatable in an up/down direction. In addition, the hydraulic excavator has an operator's cab in the front of the upper structure, a counter weight in the rear of the same, and an engine room between the operator's cab and the counter weight, that is, in front of the counterweight. An engine, a hydraulic pump, a cooling unit consisting of a plurality of heat exchangers, etc. are disposed in the engine room.
In addition, according to the background-art technique, a first vertical rib and a second vertical rib are provided on a main frame of the upper structure so as to extend in parallel with each other in a front/rear direction. The region on the main frame is divided into three regions by means of the first vertical rib and the second vertical rib. That is, the region on the main frame is divided into three regions consisting of a center region which is formed between the first vertical rib and the second vertical rib, a first side region which is formed on one side of the first vertical rib so as to be located opposite to the second vertical rib and in which the operator's cab etc. are disposed, and a second side region which is formed on the other side of the second vertical rib so as to be located opposite to the first vertical rib and in which a fuel tank etc. are disposed.
According to the background-art technique, a slewing motor for slewing the upper structure is disposed in the center region of the aforementioned three regions on the main frame, and constituted by a slewing electric motor, that is, an electric motor. A control device including an inverter for controlling the slewing electric motor and an electric storage device for storing electric power for driving the slewing electric motor are provided in the engine room and disposed in an upstream position of the cooling unit with respect to the flow of intake air introduced into the engine room.